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Zinc Nickel Plating
The preferred alloy composition of zinc nickel plate is 12 – 15% nickel, with the remainder being zinc. This alloy gives exceptional sacrificial corrosion resistance and can be readily passivated. To achieve this alloy, zinc nickel is usually plated from an alkaline electrolyte. These electrolytes have the following advantages:
- Uniform deposit thickness
- Good nickel distribution
- Excellent post plate passivation characteristics.
To meet the latest industry requirements and specifications, MacDermid have introduced Enviralloy NiFlex 12.
Applications
Zinc nickel plating is usually applied where specifiers want the highest performance with the lowest deposit thickness. By specifying zinc nickel, components can resist more than 1000 hours neutral salt spray (ISO 9227 & ASTM B117) with no effect on the dimensional tolerance of threaded components. Components typically plated with zinc nickel include:
- Automotive – Fluid transfer tubes which can be deformed into their required shape after plating
- Automotive – Fasteners, particularly in areas of high corrosion (underhood, chassis joints)
- Electronic – Connectors, as a direct replacement for cadmium to provide corrosion resistance and high electrical conductivity
- Aerospace and defense – Joining components in contact with aluminum.
To meet these industry requirements, specifiers request ZinKlad 1000. By demanding this coating, leading automotive companies receive zinc nickel plating finished by an approved applicator.
Post Plate Passivation
Zinc nickel deposits are passivated to further enhance the corrosion resistance of the deposit. Recent legislation including End of Life Vehicle Directive (ELV) and Restriction of the use of certain hazardous substances (RoHS) has led to new, high performance, passivation systems based on trivalent chromium.
Topcoats
Finally a topcoat can be applied to the zinc nickel plating and trivalent passivation coatings. The choice of topcoat depends on the application. Advantages of topcoats include:
- Predictable torque and tension characteristics
- Improved corrosion resistance after post plating deformation operations
- Resistance to thermal shock (heat exposure) testing
